Production cars use set shock absorbers and coil springs, and changing those from stock without ruining the car's ride or handling takes time, patience and expertise. And choosing a suspension kit can be a daunting task. There are a multitude of manufacturers and companies selling a wide range of components in a bewildering combination of quantity and quality.
Added to the mix is the fact that air suspension kits only replace coil springs, and coil springs are part of a larger suspension system. Given this fact, many companies offer total suspension overhaul kits, where everything from tie rods to control arms and shocks are replaced with high-end components designed to maximize what an air suspension system can offer.
However, in general, the most basic kits come with air bags to replace a vehicle's coil springs, along with a compressor and air lines. Most basic kits are a two-way system that can result in heavy body roll. Stepping up the line in price means better components, which means more control and variability, better components, and more speed in making changes.
Buying a kit should not be a casual affair. Owners need to put a lot of thought into what they want from a system. The owner of a classic El Camino show car looking to drop his suspension to new lows would need a different system than a heavy-duty pick-up driver looking for better load capacity and control when hauling tools and building material. Similarly, a race driver would be looking for a different level of performance than the driver of a touring car.
Top-of-the-line kits use a four-way system coupled with an advanced controller. Each air bag is controlled separately, but they're linked together by the electronic controller for dynamic and static control. When choosing a kit, consumers also need to understand the differences between pressure systems and ride-height systems.
Pressure-based systems monitor only the air pressure in the bag. This is fine in most cases when you want to do something like preset a pressure to lower a low-rider at a show. However, adding ride-height sensors into the electronic mix brings the kit to a new level. Ride-height systems monitor how much a car raises and lowers while monitoring the pressure needed to reach each level. Ride height and pressure come into play in performance applications as well as work applications, like keeping suspension up on a pickup truck loaded with a few tons of mulch.